Prediction and bioactivity of small-molecule antimicrobial peptides from Protaetia brevitarsis Lewis larvae

Acorus calamus as a promising source of new antibacterial agent against Pseudomonas aeruginosa and Staphylococcus aureus: Deciphering volatile compounds and mode of action

Acorus calamus is a medicinal plant known for its multifaceted health benefits, especially against inflammation and infectious ailments. In the current work, we attempt to investigate the volatile constituents of A. calamus essential oil (ACEO) and, for the first time, to elucidate its antibacterial mechanism. Gas chromatography coupled to a mass spectrometer (GC-MS) was used to investigate phytochemical substances. The GC-MS analysis detected β-asarone (71.13 %), an aromatic anisole as main component, followed by α-asarone (12.07 %), β-calacorene (3.01 %), methyl isoeugenol (2.16 %). ACEO exhibited remarkable antibacterial activity, as demonstrated by significant inhibition zones against several bacteria that were tested. Gram-positive strains, Staphylococcus aureus and Bacillus subtilis, showed inhibition zones measuring 20.11 ± 0.28 mm and 18.06 ± 1.36 mm, respectively, while Gram-negative bacteria, Pseudomonas aeruginosa, and Escherichia coli, displayed slightly smaller zones of 15.58 ± 0.68 mm and 16.00 ± 0.04 mm. The results of ACEO were competitive with Tetracycline and Cefoperazone. Furthermore, ACEO demonstrated low MICs (ranging from 0.125 % to 1.0 %) and MBCs (ranging between 0.125 % and 2.0 %), with MBC/MIC ratios consistently below 4.0, confirming its bactericidal nature. Time-kill kinetics represented high lethality of ACEO at MIC levels against Staphylococcus aureus and Pseudomonas aeruginosa, resulting in a significant reduction in colony-forming units within 12-24 h. The antibacterial mechanisms of ACEO were investigated, demonstrating its potential to disrupt the integrity of the cell membrane and enhance membrane permeability. This disruption results in the release of genetic material (RNA and DNA) and proteins from the bacterial cell. Significant anti-biofilm activity further highlights the potential of the tested compounds in combating biofilm-associated infections. Scanning electron microscopy (SEM) images revealed significant inhibition of bacterial adhesion (First step of biofilm formation) on used surface as well as possible morphological changes in bacterial cells treated with ACEO.

Exploring Tenebrio molitor as a source of low-molecular-weight antimicrobial peptides using a n in silico approach: correlation of molecular features and molecular docking

BACKGROUND

Yellow mealworm (Tenebrio molitor) larvae are increasingly recognized as a potential source of bioactive peptides due to their high protein content. Antimicrobial peptides from sustainable sources are a research topic of interest. This study aims to characterize the peptidome of T. molitor flour and an Alcalase-derived hydrolysate, and to explore the potential presence of antimicrobial peptides using in silico analyses, including prediction tools, molecular docking and parameter correlations.

RESULTS

T. molitor protein was hydrolysed using Alcalase, resulting in a hydrolysate (TMH10A) with a 10% degree of hydrolysis. The peptidome was analysed using LC-TIMS-MS/MS, yielding over 6000 sequences. These sequences were filtered using the PeptideRanker tool, selecting the top 100 sequences with scores >0.8. Bioactivity predictions indicated that specific peptides, particularly WLNSKGGF and GFIPYEPFLKKMMA, showed significant antimicrobial potential, particularly against bacteria, fungi and viruses. Correlations were found between antifungal activity and physicochemical properties such as net charge, hydrophobicity and isoelectric point.

CONCLUSIONS

The study identified specific T. molitor-derived peptides with strong predicted antimicrobial activity through in silico analysis. These peptides, particularly WLNSKGGF and GFIPYEPFLKKMMA, might offer potential applications in food safety and healthcare. Further experimental validation is required to confirm their efficacy. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterization of Novel Plantaricin-Derived Antiviral Peptides Against Flaviviruses

Flaviviruses, including West Nile virus, Zika virus, and Dengue virus, pose global health challenges due to their distribution, pathogenicity, and lack of effective treatments or vaccines. This study investigated the antiviral activity of novel truncated peptides derived from the two-peptide plantaricins PLNC8 αβ, PlnEF, PlnJK, and PlnA. The antiviral potential was predicted using machine learning tools, followed by in vitro evaluation against the Kunjin virus using plaque reduction assays in Vero cells. Molecular docking assessed peptide interactions with KUNV and ZIKV. Full-length and truncated peptides from PlnA, PlnE, PlnF, PlnJ, and PlnK demonstrated limited antiviral efficacy against KUNV in vitro, despite in silico predictions suggesting antiviral potential for PlnA, PlnE, and PlnJ. Large discrepancies were observed between the predicted and experimentally determined activities. However, complementary two-peptide plantaricins PlnEF and PlnJK exhibited significant synergistic effects. Furthermore, the truncated peptides PLNC8 α1-15 and PLNC8 β1-20 reduced KUNV viral load by over 90%, outperforming their full-length counterparts. Molecular docking revealed interactions of PLNC8 α and PLNC8 β, and their truncated variants, with KUNV and ZIKV, suggesting a mechanism involving viral envelope disruption. These findings highlight the potential of plantaricin-derived peptides as promising antiviral candidates against flaviviruses, warranting further investigation into their mechanisms and applications.

Protaetia brevitarsis Hydrolysate Mitigates Muscle Dysfunction and Ectopic Fat Deposition Triggered by a High-Fat Diet in Mice

BACKGROUND/OBJECTIVES

Obesity is a key factor in metabolic syndrome (MetS) development. Consumption of a high-fat diet (HFD) accelerates the onset of obesity and associated metabolic complications. Protaetia brevitarsis (PB) has been traditionally utilized in Korean medicine for its antioxidant, anti-diabetic, anticancer, and hepatoprotective effects. However, specific effects of PB hydrolysate on skeletal muscles have not been fully elucidated. Therefore, this study sought to assess the influence of PB on HFD-induced MetS, focusing on the lipid metabolism and inflammatory responses mediated by AMP-activated protein kinase activation.

METHODS

To induce obesity, 6-week-old C57BL/6J mice were maintained on an HFD for 8 weeks, after which PB hydrolysate was orally administered for 16 weeks while the HFD regimen was sustained. A glucose tolerance test was conducted orally to evaluate glucose regulation, and forelimb grip strength was assessed upon completion of the experimental period. Histological assessments, serum biochemical analysis, lipid extraction, Western blot analysis, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) were performed following euthanasia.

RESULTS

PB significantly reduced ectopic lipid deposition in skeletal muscles, enhanced muscle strength, and improved insulin sensitivity by increasing fatty acid oxidation via AMP-activated protein kinase/carnitine palmitoyltransferase 1 activation and inhibiting lipogenesis via stearoyl-CoA desaturase 1 gene downregulation. Furthermore, PB alleviated HFD-induced low-grade chronic inflammation by decreasing systemic monocyte chemoattractant protein 1 levels, thereby reducing ectopic fat deposition.

CONCLUSIONS

This study highlights the potential of PB as a nutraceutical to mitigate MetS in HFD-fed mice.

Biological Properties of S. warneri KYS-164 Isolated from Kefir Grains

Staphylococcus worderi KYS-164, isolated from homemade Tibetan kefir grains, produces bacteriocin-like inhibitory substances (BLIS), which are peptides with antimicrobial properties, but have not been fully characterized. The research on BLIS will lay the foundation for mining new bacteriocins. In this study, the optimal culture conditions for the production of highly active BLIS were found to be incubation at 30 °C and 120 rpm, and the most effective extraction method was ammonium sulfate precipitation (ASP) using ammonium sulfate at 80% saturation. The postantibiotic effect (PAE) of BLIS on Staphylococcus aureus CICC 10384 is significant, with a 4 × MIC BLIS concentration able to prolong the PAE to 2.39 h. BLIS has excellent biosafety, with no deleterious effects observed at 8 × MIC concentration. Gas chromatography-ion mobility spectrometry (GC-IMS) was used to analyze the volatile compounds synthesized by Staphylococcus warneri KYS-164 during its growth. Hydroxycitronellal, ethyl pyruvate, and α-pinene were found to be unique substances produced by this strain, which can provide fresh, refreshing floral and fruity aromas as well as strong pine and resinous aromas in the process of kefir grain fermentation of milk. Analysis of the S. warneri KYS-164 genome provided insights into the major metabolic pathways in which genes expressed in this strain are involved. This study represents the first isolation of S. warneri KYS-164 from kefir grains prepared by Tibetan families, and provides a comprehensive analysis of its physicochemical properties. This research provides a solid foundation for better understanding and utilization of S. warneri KYS-164.

Antibacterial peptides from black soldier fly (Hermetia illucens) larvae: mode of action and characterization

Antibacterial peptides from black soldier fly larvae extract were prepared using Flash column chromatography. Three out of five fractions (F2, F3 and F4) showed antibacterial activity against Listeria monocytogenes DMST 17303 with a minimum inhibitory concentration (MIC) of 1 mM, followed by Salmonella enterica Enteritidis DMST 15679 and Escherichia coli O157:H7 DMST 12743 with a MIC ranging from 4 to 8 mM. Due to the higher yield, F2 and F3 were further analyzed on their mode of action against L. monocytogenes DMST 17303. Both fractions, particularly F2, exerted antibacterial activity through inducing bacterial cell membrane disintegration and interaction with intracellular compounds including fatty acids, proteins, and nucleic acids. The F3 did not show significant hemolytic activity up to 4 mM, while F2 showed lower than 5% hemolysis up to 8 mM. Time-to-kill analysis revealed that F2 was more effective and exerted a sustainable killing effect after 2 and 4 h, depending on the concentration of 1 and 2×MIC, respectively, while the F3 at 2×MIC could completely kill the test bacteria within 24 h. Among the identified peptides in the fractions, those with charged, either positively or negatively, and moderate hydrophobicity of ranging 6.68-15.70, namely CGPPRQGPFPR, HLEEELK, LEEAEERAD, TEELEEAKKK, and KGNSELEEAKKK, are potential antimicrobial peptides.

Capping motifs in antimicrobial peptides and their relevance for improved biological activities

N-capping (N-cap) and C-capping (C-cap) in biologically active peptides, including specific amino acids or unconventional group motifs, have been shown to modulate activity against pharmacological targets by interfering with the peptide's secondary structure, thus generating unusual scaffolds. The insertion of capping motifs in linear peptides has been shown to prevent peptide degradation by reducing its susceptibility to proteolytic cleavage, and the replacement of some functional groups by unusual groups in N- or C-capping regions in linear peptides has led to optimized peptide variants with improved secondary structure and enhanced activity. Furthermore, some essential amino acid residues that, when placed in antimicrobial peptide (AMP) capping regions, are capable of complexing metals such as Cu2+, Ni2+, and Zn2+, give rise to the family known as metallo-AMPs, which are capable of boosting antimicrobial efficacy, as well as other activities. Therefore, this review presents and discusses the different strategies for creating N- and C-cap motifs in AMPs, aiming at fine-tuning this class of antimicrobials.

Jelleine, a Family of Peptides Isolated from the Royal Jelly of the Honey Bees (Apis mellifera), as a Promising Prototype for New Medicines: A Narrative Review

The jelleine family is a group of four peptides (jelleines I-IV) originally isolated from the royal jelly of honey bee (Apis mellifera), but later detected in some honey samples. These oligopeptides are composed of 8-9 amino acid residues, positively charged (+2 to +3 at pH 7.2), including 38-50% of hydrophobic residues and a carboxamide C-terminus. Jelleines, generated by processing of the C-terminal region of major royal jelly proteins 1 (MRJP-1), play an important biological role in royal jelly conservation as well as in protecting bee larvae from potential pathogens. Therefore, these molecules present numerous benefits for human health, including therapeutic purposes as shown in preclinical studies. In this review, we aimed to evaluate the biological effects of jelleines in addition to characterising their toxicities and stabilities. Jelleines I-III have promising antimicrobial activity and low toxicity (LD50 > 1000 mg/Kg). However, jelleine-IV has not shown relevant biological potential. Jelleine-I, but not the other analogues, also has antiparasitic, healing, and pro-coagulant activities in addition to indirectly modulating tumor cell growth and controlling the inflammatory process. Although it is sensitive to hydrolysis by proteases, the addition of halogens increases the chemical stability of these molecules. Thus, these results suggest that jelleines, especially jelleine-I, are a potential target for the development of new, effective and safe therapeutic molecules for clinical use.

Identification, characterization and hypolipidemic effect of novel peptides in protein hydrolysate from Protaetia brevitarsis larvae

The proteins were mainly derived from Protaetia brevitarsis larval extracts obtained using two empty intestine methods (traditional static method: TSM or salt immersion stress method: SISM) and extraction solvents (water: W or 50 % water-ethanol: W:E), and the proteins were used as objects to investigate the effect of emptying intestine methods on hypolipidemic peptides. The results revealed that the F-2 fractions of protein hydrolysate had stronger in vitro hypolipidemic activity, with the peptides obtained by SISM possessing a stronger cholesterol micelle solubility inhibition rate, especially in SISM-W:E-P. Moreover, a total of 106 peptides were tentatively identified, among which SISM identified more peptides with an amino acid number < 8. Meanwhile, five novel peptides (YPPFH, YPGFGK, KYPF, SPLPGPR and VPPP) exhibited good hypolipidemic activity in vitro and in vivo, among which YPPFH, VPPP and KYPF had strong inhibitory activities on pancreatic lipase (PL) and cholesteryl esterase (CE), and KYPF, SPLPGPR and VPPP could significantly reduce the TG content in Caenorhabditis elegans. Thus, P. brevitarsis can be developed as a naturally derived hypolipidemic component for the development and application in functional foods.